As I understand it the value inside @myDoc.query('/Root/ProductDescription/Features') part is the XPath address so the problem should be the XML(presumably the XPath) and not the SQL

It seems like it fails because I added a xmlns="..." xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="....", because it now has a namespace I assume I have to edit the XPath to make it correct? but how?